How to solve the vibration phenomenon of the water pump
The cause of vibration of the water pump and the result of the modification. Water pump is a machine that conveys liquid or pressurizes liquid. It transfers the mechanical energy of the prime mover or other external energy to the liquid to increase the energy of the liquid. It is mainly used to transport liquids including water, oil, acid and alkali liquids, emulsions, suspoemulsions and liquid metals, etc. It can also transport liquids and gas mixtures. And liquids containing suspended solids. The technical parameters to measure the performance of water pumps include flow, suction, head, shaft power, water power, efficiency, etc.; according to different working principles, they can be divided into volumetric pumps, vane pumps and other types. Positive displacement pumps use the change in the volume of their working chambers to transfer energy; vane pumps use the interaction between rotating blades and water to transfer energy. There are centrifugal pumps, axial flow pumps and mixed flow pumps.
1. Analysis of the causes of pump vibration
1. The domestic vertical water pump 28SLA-10 is directly transformed from a horizontal pump. The vertical height between the motor base and the water pump base is 4.3m, and the drive shaft system weighs 3t. Compared with the horizontal pump, it adds an intermediate drive shaft with a length of 3752mm and a diameter of 140mm. In terms of structure, apart from installing a bearing on the intermediate drive shaft, no modification has been made. The operating pressure of these four water pumps is 0.7～0.85MPa for a long time. Under the conditions of high lift and large flow, such a system with high center of gravity and high mass rotates at high speed, the centrifugal force generated is very large, which will cause the unit to be larger. vibration. In addition, the rigidity of the connection between the bracket and the water pump in the water inlet and outlet directions is insufficient, resulting in a large displacement of the water pump and the connecting parts. The displacement of the water pump during operation causes the stress condition of the upper bearing to change, and the vibration increases, so it is easy to generate heat. If the displacement of the pump is corrected and the bearing conditions are improved, the vibration intensity of the system can be reduced.
2. There is a rigid connection between the water pump and the drive shaft. Due to manufacturing and installation reasons, the pump shaft is concentric with the drive shaft during operation, causing the pump to vibrate; the vibration generated by the motor, drive shaft and other sources is also directly transmitted to the pump, forming a superposition of vibrations, and further increasing the pump vibration. In addition, this kind of rigid connection increases the external force that the bearing on the water pump bears, causing the bearing to easily generate heat and affect the pump shaft.
2. Reconstruction situation In response to the above reasons, we took the following two steps to rebuild.
1. Strengthen the rigidity of the pipeline. Considering that it is difficult to reinforce the water pump, the method of welding "reinforcing ribs" at the outlet of the water pump is adopted. Along the water inlet and outlet directions, the flanges at both ends of the connecting steel pipe between the divergent pipe of the water pump outlet and the water outlet valve are welded with 8 steel plates with a thickness of 32mm and a width of 100mm. Increase the rigidity of the steel pipe, reduce the amount of deformation, and resist the displacement of the water pump. After measurement, after reinforcement, the displacement of point A of the water pump drops to 0.35mm.
2. Transform the transmission system. In order to reduce the transmission of vibration of the motor and drive shaft to the water pump, the rigid connection between the water pump and the drive shaft is changed to an elastic connection. Using GB4323-84 elastic sleeve pin coupling, the maximum compensation displacement of the centrifugal pump is 0.6mm, and the compensation angle is 1°30°. In this way, the vibration of the motor and the transmission shaft can be compensated by the elastic coupling and will not be directly transmitted to the water pump.
3. Transformation results After the transformation, after measurement, the pump vibration was reduced from the vibration speed of 4.3cm/s before the transformation to 1.48cm/s. According to the vibration intensity standard ISO2372-1974, it can be determined that the pump operation is in the excellent zone. At the same time, the pump runs smoothly, the upper bearing only needs to be maintained normally, and the pump shaft is no longer worn, indicating that the transformation is successful. Briefly describe the structure and advantages of the water jet: The water jet consists of a body, a cover, a nozzle, a nozzle seat plate, a guide plate, a diffuser tube and a one-way valve. The nozzle adopts a multi-nozzle structure. , In order to obtain a larger water vapor contact area, which is conducive to heat exchange and obtains a better vacuum effect. The nozzle seat plate is processed precisely and has high precision, so that the jet water flow is deflected and the pumping efficiency is reduced. The whole device has a compact and precise structure and high strength. It is used in a vacuum evaporation system. Since the condensation effect of the condenser and the pumping effect of the vacuum pump can be combined in one device, the process flow is greatly simplified. The use of vacuum pumps and old condensers can save equipment such as vacuum pumps, condensers, and water separators, and has the following advantages:
(1) The hydraulic ejector is small in size, light in weight and compact in structure. And the efficiency is relatively high, the power consumption is lower than the vacuum pump system, and the investment is low.
(2) The operation is simple and the maintenance is convenient, and there is no need for full-time personnel management. Because there is no mechanical transmission part, the noise is low and no lubricating oil is consumed.
(3) It can be installed at the bottom outdoor, with less floor space, which can save the construction area and installation cost of the plant. A hydraulic ejector is a mechanical device with three effective functions such as vacuuming, condensation and drainage. It uses a certain pressure of water to circulate symmetrically and evenly distributed in a certain inclination nozzles to spray out, converge on a focal point. Due to the high velocity of the jet water flow, negative pressure is formed around the chamber to generate a vacuum. In addition, because the secondary steam directly contacts the jet water flow for heat exchange, most of the steam is condensed into water, and a small amount of uncondensed steam and non-condensed steam The condensed gas is also mixed and squeezed due to friction with the high-speed jet of water, and is eliminated through the diffuser tube, so that a higher vacuum is formed in the chamber. The application of hydraulic ejector is extremely wide. It is mainly used in vacuum and evaporation systems for vacuum pumping, vacuum evaporation, vacuum filtration, vacuum crystallization, drying, deodorization and other processes. It is used for sugar, pharmaceutical, chemical, food, salt, monosodium glutamate, milk , Fermentation and some equipment widely required by light industry and national defense departments. However, the current manufacturing plant for producing water jets is relatively small and the varieties are not complete. For this reason, the design has been continuously improved in recent years, and the structure of multi-jet resistance and steam ring (guide plate) is adopted, and the water is fed by multi-stage pumps. Installation only needs to be installed at a height of 4.5 meters, which improves and improves its working performance. It has a certain advanced nature and is an innovation of vacuum condensing equipment.
